This invention relates to container lids attachable to tubular containers by means of induction heating, the lids also being stackable one atop another prior to use.
Tubular containers find use throughout the packaging industry and provide a robust container useful in a broad range of applications to hold a wide variety of bulk goods including foodstuffs, hardware and chemicals to cite only a few examples.
It is often desirable that the container have a lid construction which initially provides a hermetic seal for the container, the seal preventing air and moisture from entering the container and adversely affecting its contents. This feature is especially important for food stuffs, such as cereals, which must remain fresh between the time of packaging and purchase by the consumer.
It is also advantageous that the lid have a readily visible feature which provides a permanent indication once the lid has been opened. This xe2x80x9ctamper evident featurexe2x80x9d permits consumers to judge at a glance whether the integrity of the container has been violated and not purchase the item.
The lid should also be reclosable, enabling the container to provide convenient storage of the bulk goods, extending their shelf life and preventing inadvertent spills of the container contents. For convenience of dispensing its contents, the lid should also have a means for holding the lid in an open position until it is desired to reclose it.
The lid should also be inexpensive to produce and must attach permanently to the container if tubular containers are to be commercially acceptable with other packaging such as rectangular paperboard boxes. Traditionally, hot-melt adhesives have been used to attach such a lid to the tubular container, but a lid which obviates the use of such adhesives is desirable for several reasons. First, the costs of the adhesive and the machinery needed to apply it increase the costs of such packages to such an extent as to make their use on a large scale economically unfeasible. Second, it is also disadvantageous to fill the container and then secure the lid with hot melt adhesive due to the potential for contamination of the container contents with the adhesive or spillage of the contents onto the machinery applying the hot melt.
The lid for a tubular container should also be easy to handle by automated machinery for assembly of the container. The lid should be reliably stackable to permit large numbers to be shipped efficiently and loaded into the processing machines for assembly of the container.
There is clearly a need for a reclosable lid for tubular containers which can provide a hermetic seal, a tamper-evident feature, be permanently attached and yet be inexpensive enough to allow tubular containers to compete economically with other forms of packaging.
The invention concerns a lid for a container having a sidewall with a rim defining an opening into the container. The lid is engageable with the rim to close the opening. In its preferred embodiment, the lid comprises a central panel having an outer perimeter and a hinge extending transversely across the central panel and dividing the lid into two lid portions. One lid portion is pivotably movable about the hinge relatively to the other lid portion.
The lid also has a resilient, flexible skirt joined to its perimeter, the skirt extending substantially perpendicularly to the plane of the central panel. The skirt has an inside surface which is positionable to face the container sidewall adjacent to the rim and a pair of weakened regions arranged on opposite sides of the lid. The weakened regions are aligned with the hinge and are subject to failure to facilitate separation of the skirt at the hinge when the one lid portion is pivoted relatively to the other lid portion. Preferred material for the central panel is paperboard and plastic resin for the lid.
A detent projects substantially perpendicularly from the inside surface of the skirt on the one lid portion. Preferably, the detent is positioned adjacent to one of the weakened regions. The detent is resiliently biasable into engagement with the rim by the skirt, and when the lid is engaged with the rim, the detent cooperates with the rim to hold the one lid portion in a pivoted position relatively to the other lid portion, thereby exposing the opening in the container.
Preferably, the lid has a stacking lip making the lid stackable with another substantially identical lid. The stacking lip is joined to the perimeter of the central panel and extends substantially perpendicularly to the plane of the central panel away from the skirt. The lip is engageable with an inside surface of a skirt on the other substantially identical lid for stacking the lids one atop the other. The lip has a notch aligned with the hinge and sized to receive a detent on the other substantially identical lid. Preferably, the stacking lip is formed integrally with the skirt.
For facilitating pivoting of the one lid portion relatively to the other, the lid has two elongated cuts through the central panel. The cuts are positioned coincident with and along the hinge adjacent to a respective weakened region. The lid also has two elongated tabs, each one being attached to the central panel and covering one of the elongated cuts for sealing the central panel. Preferably, the elongated tabs are integrally formed with the skirt.
To provide a hermetic seal to the container, the lid has a membrane overlying the central panel adjacent to the inside surface of the skirt. The membrane is positionable in overlying registration with the opening and attachable to the rim for sealing the container opening.
Preferably, the membrane is a metal foil which allows it to be attached to the container by a heat activated adhesive and an induction heating process. The membrane has a first heat activated adhesive layer on a first side thereof, the first side being positionable to face the rim. The first adhesive layer is engageable with the rim to attach the membrane to the rim and thereby enclose the opening when the lid is engaged with the rim.
A second heat activated adhesive layer is positioned on a second side of the membrane opposite to the first side. The second adhesive layer is positioned to engage the other lid portion for attaching the lid to the rim when the lid is engaged with the rim.
The invention also contemplates a container and a lid as described above. The container has a sidewall defining an interior space and an opening providing access to the space. A rim surrounds the opening and the lid is engaged with the rim in overlying registration with the opening.
The container is sealed by a membrane positioned between the lid and the rim, the membrane being in overlying registration with the opening and attached to the rim, thereby sealing the opening.
Attachment of the membrane is preferably via a first adhesive layer positioned between the membrane and the rim. To attach the lid to the container, a second adhesive layer is positioned between the membrane and the other lid portion.
It is an object of the invention to provide a lid for a tubular container which is easily openable and reclosable.
It is another object of the invention to provide a lid which will remain opened for convenience of dispensing the container contents.
It is still another object of the invention to provide a lid which has a readily visible tamper evident feature.
It is yet another object of the invention to provide a lid which can effect an initial hermetic seal of the container.
It is again another object of the invention to provide a lid which may be attached to the container by induction heating means and avoid the use of liquid hot melt adhesives.
It is yet again another object of the invention to provide a lid which is stackable with substantially identical lids.
It is still another object of the invention to provide a lid which can be handled by automated equipment to assemble a container.
It is furthermore an object of the invention to provide a lid which will improve the economic feasibility of tubular containers.
These as well as other objects and advantages of the invention will become apparent from consideration of the following drawings and detailed description of the preferred embodiment.